In most of today's wind turbines the drive unit is placed in a nacelle, which also carries the wind turbine rotor. The nacelle is necessarily arranged on top of a high mast and rotates so that the rotor is always facing the wind.
Such placement of the drive unit results in a great weight at the top of the mast and that access for maintenance is a challenge. Yet it is this position of the drive unit and the generators that are used extensively as the alternative that the rotational torque must be transmitted via a shaft through the mast. This leads to losses and requires that the mast can absorb the reaction torque from the rotation shaft.
There is an urgent need to simplify the drive unit and make it lighter. There is also a need to make access for maintenance easier. These are the main aims of the present invention, and are achieved by the features that appear in the claims and described herein.
A drive unit for a wind turbine is described in publication WO2010/086362. This prior art relates to a wind turbine drive which uses belts to transmit the rotation from the rotor to a generator.
It is well known from WO 2008/028335 and JP2005023893 to use a belt to transmit the rotation from the rotor to a generator. However, the present invention aims to utilize the characteristics of the belt operation, or possibly the chain operation, better so that a more compact drive device could be achieved with additional operational benefits.
None of the abovementioned publications shows a drive unit with a planetary belt carrier with belt pulleys which are in rotational coupling with a stationary mounted large belt. The belt pulleys are also in rotational coupling with a shaft connected to the driven unit or a drive unit.